Operation of Wideband Code Division Multiple Access (WCDMA) and/or High Speed Packet Data Access (HSPA) on multiple 5 MHz frequency blocks, or carriers as they also may be referred to, is one further step of evolving WCDMA and HSPA. This mode of operation is often referred to as Multi Carrier WCDMA or Multi Carrier HSPA, in the following referred to as “multi carrier HSPA”.
A multi carrier (MC) arrangement with Frequency Division Duplex (FDD) can be described as a set of downlink carriers linked to a set of uplink carriers. The downlink carriers can be adjacent or non-adjacent in the frequency domain, and the same holds for the uplink carriers. More general, carriers do not need to be in the same band and Time Division Duplex (TDD) bands could also be used as part of the multi carrier operation.
The multi carrier arrangements can also be such that the number of downlink carriers is different from the number of uplink carriers.
One concept to arrange the uplink and downlink carriers in a multi carrier system would be to define an anchor (A) carrier in uplink and downlink. The remaining carriers, both uplink and downlink carriers, in the multi carrier system can be referred to as non-anchor (NA) carriers. For example, most of the control signalling can be carried on the anchor carrier, while the non-anchor carriers carry only the data channels and necessary control signalling channels that cannot be carried on the anchor carrier.
For example, two 5 MHz downlink carriers can be placed as one carrier in the 850 MHz band and one carrier in the 1900 MHz band respectively. For the case when the downlink carriers are in multiple bands, the user equipment (UE) needs to have support for receiving signals on two downlink bands simultaneously.
The uplink may reside in either of the bands or even transmission on two uplinks is possible. Similar to the downlink, the user equipment needs to have support for transmitting signals on two uplink bands simultaneously.
Support for receiving or transmitting signals simultaneously on two bands is very costly for a user equipment implementation, as it requires doubled Radio Frequency (RF) chains. Also, the simultaneous signalling over two or more bands is energy consuming.
The same problems are valid for multicarrier configurations in more than two bands.